The main difference is that the 680i, has more features than, the 650i cipset....more expensive though. The 680i compared to the 650i, usually have 2 or more USB & SATA ports, dual gigabit LAN, SLI x16 compared to 650i's SLI x8. With SLI, the 650i, was shown that even running SLI in x8, it's equal if not better than the 680i, in SLI performance.